Campbell Biology: Concepts & Connections Tenth Edition Chapter 2 PDF

Campbell Biology: Concepts & Connections Tenth Edition Chapter 2 The Chemical Basis of Life Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Introduction How might a chemical compound in the air harm coral reefs? T...

Campbell Biology: Concepts & Connections Tenth Edition Chapter 2 The Chemical Basis of Life Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Introduction How might a chemical compound in the air harm coral reefs? The answer is chemistry. – When carbon dioxide (C O2) dissolves in water, it reacts with water to form an acid, which can disrupt the formation of coral skeletons. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.0_0 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.0_1 (1 of 2) Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Elements, Atoms, and Compounds Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.1 Organisms Are Composed of Elements, Usually Combined into Compounds (1 of 2) Living organisms are composed of matter. Matter is composed of chemical elements. – About 25 elements are essential for human life. – Four elements make up about 96% of the weight of most living organisms. A compound is a substance consisting of two or more different elements in a fixed ratio. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.1 Organisms Are Composed of Elements, Usually Combined into Compounds (2 of 2) Checkpoint question Explain how table salt illustrates the themes of emergent properties. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.1b Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.2 Connection: Trace Elements Are Common Additives to Food and Water (1 of 2) Some trace elements are required to prevent disease. Fluoride is usually added to municipal water and dental products to help reduce tooth decay. Several chemicals are added to food to – help preserve it, – make it more nutritious, and/or – make it look better. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.2 Connection: Trace Elements Are Common Additives to Food and Water (2 of 2) Checkpoint question A serving of cereal fortified to provide 100% of the recommended daily intake contains 18 m g of iron. The recommended tolerable upper intake level is 45 m g (before causing gastrointestinal upset). How many bowls of cereal can you eat before you exceed that level? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.2a Goiter: Iodine defiency Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.2b Foods rich in Iron Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.2c Flouride added to toothpaste and mouthwash Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.3 Atoms Consist of Protons, Neutrons, and Electrons (1 of 2) Each element consists of one kind of atom. An atom is the smallest unit of matter that still retains the properties of an element. Three subatomic particles are relevant to our discussion of elements. – Neutrons and protons are packed into an atom’s nucleus. – Electrons orbit the nucleus. The unique number of protons is an element’s atomic number. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.3 Atoms Consist of Protons, Neutrons, and Electrons (2 of 2) An atom’s mass number is the sum of its protons and neutrons in the nucleus. The atomic mass is approximately equal to its mass number. Isotopes of an element have the same number of protons but different numbers of neutrons. Molecules = two or more atoms combined. Ex. O2 Compound = defined number of atoms in defined spatial relationship (Combination of elements with a defined ratio) Ex: NaCl, H20, H2S04 Copyright © 2020 Pearson Education, Inc. All Rights Reserved.  Atoms whose shells are not full tend to interact with other atoms and gain, lose, or share electrons Valence Electrons: # of electrons in outer shell Outermost electron shell (can hold 8 electrons) Electron First electron shell (can hold 2 electrons) HYDROGEN (H) CARBON (C) NITROGEN (N) OXYGEN (O) Atomic number = 1 Atomic number = 6 Atomic number = 7 Atomic number = 8 Valence =1 Valence=4 Valence = 5 Valence = 6 Figure 2.6 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.3 Helium Atomic structure Copyright © 2020 Pearson Education, Inc. All Rights Reserved.  Carbon Atom = electrons - Electronegative charge - 1/1840 amu = protons - electrons travel in - Positively charged regions outside the - 1 amu nucleus called orbitals = neutrons Nucleus _______________= - No charge center of an atom. - 1 amu Home to protons and neutrons. He p35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Each atom is held together by attractions between the positively charged protons and negatively charged electrons Neutrons are electrically neutral 6 Protons Nucleus 6 Neutrons 6 Electrons Figure 2.4B B. Carbon atom Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Reading the Periodic Table Example: The element Carbon (only made of carbon atoms) Atomic number = Number of protons in an atom; different SYMBOL ____________ for each element usually 1-2 letters ____________ NAME of the element _______________= MASS NUMBER # Protons + # neutrons in an atom; the average of one elements isotopes Isotopes of C p36 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 2.3 Isotopes of Carbon Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.4 Connection: Radioactive Isotopes Can Help or Harm Us Radioactive isotopes are useful as tracers for monitoring the fate of atoms in living organisms. Sophisticated imaging instruments can detect them. There are also dangers associated with using radioactive substances. Checkpoint question Why are radioactive isotopes useful as tracers in research on the chemistry of life? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.4a Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.4b Copyright © 2020 Pearson Education, Inc. All Rights Reserved.  Chemical Bonds supplemental video Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.5 The Distribution of Electrons Determines an Atom’s Chemical Properties (1 of 2) Electrons can be located in different electron shells, each with a characteristic distance from the nucleus. An atom whose outer electron shell is not full tends to interact with other atoms and share, gain, or lose electrons, resulting in attractions called chemical bonds. The number of electrons in the outermost shell is the valence number Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.5 The Distribution of Electrons Determines an Atom’s Chemical Properties (2 of 2) The actual transfer of an electron between atoms results in an attraction called an ionic bond. In a covalent bond, atoms do not transfer electrons but actually share electrons between them. https://mediaplayer.pearsoncmg.com/assets/secs-campbell-electron-arrangement Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.5a Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.5b Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.6 Visualizing the Concept: Covalent Bonds Join Atoms into Molecules Through Electron Sharing In a nonpolar covalent bond, electrons are shared equally. In polar covalent bonds, such as those found in water, electrons are pulled closer to the more electronegative atom. Checkpoint question Polarity refers to a separation of charges (think of the positive and negative poles of a battery). Explain why the bonds in a water molecule are polar covalent bonds. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.6_1 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.6_2 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.6_2c Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.7 Ionic Bonds are Attractions Between Ions of Opposite Charge An ion is an atom or molecule with an electrical charge resulting from gain or loss of one or more electrons. Two ions with opposite charges attract each other. – When the attraction holds the ions together, it is called an ionic bond. – Salt is a synonym for an ionic compound. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.7a_1 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.7a_2 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.7b_1 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Animation: Ionic Bonds https://mediaplayer.pearsoncmg.com/assets/sec s-campbell-ionic-bonds supplemental video: covalent vs. ionic bonds Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.8 Hydrogen Bonds are Weak Bonds Important in the Chemistry of Life One of the most important types of weak bonds is the hydrogen bond (one molecule is usually, but not always, contains H as the positive end). The hydrogen atoms of a water molecule are attached to oxygen by polar covalent bonds. Because of these polar bonds and the wide V shape of the molecule, water is a polar molecule. Water has an unequal distribution of charges. Checkpoint question What enables neighboring water molecules to hydrogen-bond to one another? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.8 Note 4 H-bonds per water molecule Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.9 Chemical Reactions Make and Break Chemical Bonds The formation of water from hydrogen and oxygen is an example of a chemical reaction, breaking existing chemical bonds and forming new ones. The composition of matter is changed as bonds are broken and formed to convert reactants to products. Chemical reactions do not create or destroy matter; they only rearrange it in various ways. Checkpoint question Fill in the blanks with the correct numbers in the following chemical process: C6H12O6 + ⸺ O2 → + ⸺ CO2 + + ⸺ H2O in th fill in l in Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.9 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Water’s Life-Supporting Properties Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.10 Hydrogen Bonds Make Liquid Water Cohesive The tendency of molecules of the same kind to stick together is cohesion. Ex: Water to water The clinging of one substance to another is adhesion. Ex: Water to glass Cohesion is related to surface tension—a measure of how difficult it is to break the surface of a liquid. Molecules of water undergo slightly different bonding at the interface of air and water and create tension. Checkpoint question After a hard workout, you may notice “beads” of sweat on your face. Can you explain what holds the sweat in droplet form on your face? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.10 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Animation: Water Transport Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.11 Water’s Hydrogen Bonds Moderate Temperature Thermal energy is the energy associated with the random movement of atoms and molecules. – Thermal energy in transfer from a warmer to a cooler body of matter is defined as heat. (Heat is the amount of energy in a certain substance due to the movement of molecules in a body of matter.) – Temperature measures the intensity of heat - average speed of molecules rather than the TOTAL amount of heat energy in a body of matter. Temperature and heat are related, but different. Example #1: A swimmer crossing San Francisco Bay has a higher temperature than the water, but the bay contains far more heat because of its immense volume. Example #2: A lake may have more heat in it than a glass of water but still have a lower temperature. Copyright © 2020 Pearson Education, Inc. All Rights Reserved.  When a substance evaporates, the surface of the liquid that remaining behind cools down; this is the process of evaporative cooling. This occurs because the molecules with the greatest energy (the “hottest” ones) tend to vaporize first. On a larger scale, surface evaporation cools tropical oceans. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.12 Ice Floats Because It Is Less Dense than Liquid Water Water can exist as a gas, liquid, or solid. Water is less dense as a solid than a liquid because of hydrogen bonding. When water freezes, each molecule forms a stable hydrogen bond with its neighbors. – As ice crystals form, the molecules are less densely packed than in liquid water. – Because ice is less dense than water, it floats. Checkpoint question Explain how freezing water can crack boulders. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.12 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.13 Water is the Solvent of Life A solution is a liquid consisting of a uniform mixture of two or more substances. Water’s versatility as a solvent, a dissolving agent, results from the polarity of its molecules. Polar or charged solutes dissolve when water molecules surround them, forming aqueous solutions. Checkpoint question Why are blood and most other biological fluids classified as aqueous solutions? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.13 NaCl dissociates in water Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.14 The Chemistry of Life Is Sensitive to Acidic and Basic Conditions In liquid water, a very small percentage of water molecules break apart into ions. H+ and OH- → H2O We use the pH scale to describe how acidic or basic a solution is. A buffer minimizes changes in p H. Checkpoint question Compared to a basic solution at pH 9, the same volume of an acidic solution at pH 4 has fill in the times more H+. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.14 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.14_3 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Ionic solutions Ionic compounds dissociate in water to become their individual ions. Note how H’s of water are nearest Cl- and O of water is nearest Na+ Solute: Solvent: Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.15 Scientific Thinking: Scientists Study the Effects of Rising Atmospheric CO2 on Coral Reef Ecosystems (1 of 4) Carbon dioxide is – the main product of fossil fuel combustion, – increasing in the atmosphere, and – linked to global climate change. About 25% of this human-generated CO2 is absorbed by the vast oceans. CO2 dissolved in seawater lowers the pH of the ocean in a process known as ocean acidification. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.15 Scientific Thinking: Scientists Study the Effects of Rising Atmospheric CO2 on Coral Reef Ecosystems (2 of 4) As seawater acidifies, the extra hydrogen ions (H +) combine with carbonate ions (CO32−) to form bicarbonate ions (HCO3−). This reaction reduces the carbonate ion concentration available to corals and other shell-building animals. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.15 Scientific Thinking: Scientists Study the Effects of Rising Atmospheric CO2 on Coral Reef Ecosystems (3 of 4) In a controlled experiment, scientists looked at the effect of decreasing carbonate ion concentration on the rate of calcium deposition by reef organisms. The lower the concentration of carbonate ions, the lower the rate of calcification, and thus the slower the growth of coral animals. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.15 Scientific Thinking: Scientists Study the Effects of Rising Atmospheric CO2 on Coral Reef Ecosystems (4 of 4) Source: Adaptation of figure 5 from “Effect of Calcium Carbonate Saturation State on the Calcification Rate of an Experimental Coral Reef” by C. Langdon, et al., from Global Biogeochemical Cycles, June 2000, Volume 14(2). American Geophysical Union. Checkpoint question Identify the independent and dependent variables in the experiment depicted in Figure 2.15A. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.15b Ocean Acidification Video Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 2.16 Evolution Connection: The Search for Extraterrestrial Life Centers on the Search for Water The emergent properties of water support life on Earth and may contribute to the potential for life to have evolved on other planets. Checkpoint question Why is the presence of water important in the search for extraterrestrial life? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. You Should Now Be Able to (1 of 2) 1. Describe the importance of chemical elements to living organisms. 2. Explain the formation of compounds. 3. Describe the structure of an atom. 4. Distinguish between ionic, hydrogen, and covalent bonds. 5. Define a chemical reaction and explain how it changes the composition of matter. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. You Should Now Be Able to (2 of 2) 6. List and define the life-supporting properties of water. 7. Explain the pH scale and the formation of acid and base solutions. 8. Explain how rising CO2 levels affect coral reefs. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.0 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.1a_1 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.1a_2 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.1a_3 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.U N01 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.U N02 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.U N03 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.U N03_1 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 2.U N03_2a Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Copyright This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching their courses and assessing student learning. Dissemination or sale of any part of this work (including on the World Wide Web) will destroy the integrity of the work and is not permitted. The work and materials from it should never be made available to students except by instructors using the accompanying text in their classes. 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